In wireless and wireline communication systems, a power amplifier (PA) is often included in a transmitter to amplify an output signal.
To improve power efficiency, the PA often operates near its saturation region. At the saturation region, most PA's exhibit nonlinear characteristics. PA nonlinearity also gives rise to several forms of distortion, such as harmonic distortion, spectral regrowth and intermodulation distortion. Combining with typical high peak-to-average-power modulation schemes (like Orthogonal Frequency Division Multiplexing), nonlinear distortion is a factor in the overall system design of wireless and wireline communication systems.